... At first glance, 1956 may not seem to have been a particularly bad election for Democrats. Although Republican Dwight D. Eisenhower won a predictable reelection victory in a landslide, Democrats maintained their small majorities in the House and Senate.

But they had seen a major drop in support of black and union voters, part of the backbone of the party’s coalition. Eisenhower, for instance, managed to win nearly 40 percent of black votes in 1956.

Liberals feared this shift would be permanent, robbing Democrats of a crucial base. They laid the blame at the feet of the party’s complicated national coalition.

At the time, the Democratic Party consisted of two ideological wings: a minority of (Southern) conservatives and a majority of liberals. Throughout the New Deal years, this coalition provided the party with majorities in the House, Senate and electoral college. But to keep conservatives on board, liberals had to make considerable concessions — most notably in terms of civil rights and labor issues.

By 1956, black and union voters had had enough. Liberal Democrats realized that they could no longer please Southern conservatives and Northeast liberals at the same time.

To solve this problem, liberals, including Democratic National Committee Chairman Paul Butler, used the DNC to provide a radical solution.

For the first time, the DNC claimed the right to set policy positions for the national party and used this to rebrand the Democratic Party as a solidly liberal organization, supporting civil rights, pro-union legislation, the creation of Medicaid and increased government spending.

Each of these ran counter to the wishes of Southern Democrats. But liberals thought that the greater good of the party required it to drop these voters and elected officials to remain competitive among a larger group of voters across the country. ...